1. Field of the Invention
The present invention generally relates to a liquid crystal display field, and more particularly to a liquid crystal display with a single-layer biaxial compensation architecture.
2. Description of Prior Art
With an increased viewing angle of a thin film transistor liquid crystal display (TFT-LCD), a contrast ratio of an image is decreased and clarity of the image is decreased as well. This is because a birefringence of liquid crystal molecules in a liquid crystal layer is changed with the changed viewing angle. A wide viewing angle compensation film can be used for reducing dark-state light leakage of the image, thereby increasing the contrast ratio of the image in a specific viewing angle significantly. In general, a compensation principle of the compensation film is to correct phase differences of the liquid crystal molecules at different viewing angles, such that the birefringence characteristic is compensated symmetrically.
For different liquid crystal display modes, different compensation films are utilized. A compensation film for a large-sized liquid crystal display is mostly utilized for a vertical alignment (VA) display mode. Please refer to FIG. 1. FIG. 1 shows a liquid crystal display with a single-layer biaxial compensation architecture in the prior arts. The liquid crystal display comprises a first triacetyl cellulose (hereinafter referred to as “TAC”) layer 100, a first poly vinyl alcohol (hereinafter referred to as “PVA”) layer 102, a first biaxial layer 104, a first pressure sensitive adhesive (hereinafter referred to as “PSA”) layer 106, a liquid crystal layer 120, a second PSA layer 140, a second TAC layer 142, a second PVA layer 144 and a third TAC layer 146. The liquid crystal display utilizes one biaxial layer (i.e. the first biaxial layer 104) for compensation and thus is called as a single-layer biaxial compensation architecture.
It can be known in accordance with tests that when the single-layer biaxial compensation architecture is utilized, a viewing angle at which the dark-state light leakage is serious is near a horizontal viewing angle. That is, the light leakage is concentrated between 20 degrees and 40 degrees, 140 degrees and 160 degrees, 200 degrees and 220 degrees, and 310 degrees and 330 degrees. An area near the horizontal viewing angle is easily seen by an observer, and thus the contrast ratio in the area near the horizontal viewing angle affects viewing effect most. An area near a vertical viewing angle is not easily seen by the observer, and thus the viewing effect is affected less. With the enlarged size of the liquid crystal display, the above-mentioned phenomena are more obvious. Accordingly, it is necessary to limit the area having the dark-state light leakage to the area near the vertical viewing angle instead of the area near the horizontal viewing angle in the prior arts.
Please refer to FIG. 2. FIG. 2 shows a liquid crystal display with a two-layer biaxial compensation architecture in the prior arts. The liquid crystal display comprises a TAC layer 200, a first PVA layer 202, a first biaxial layer 204, a first PSA layer 206, a liquid crystal layer 220, a second PSA layer 240, a second PSA layer 240, a second biaxial layer 242, a second PVA layer 244 and a third TAC layer 246. The liquid crystal display utilizes two biaxial layers (i.e. the first biaxial layer 204 and the second biaxial layer 242) for compensation and thus is called as a two-layer biaxial compensation architecture. When the two-layer biaxial compensation architecture as shown in FIG. 2 is utilized, the dark-state light leakage is at a viewing angle between the horizontal viewing angle and the vertical viewing angle. Although the dark-state light leakage is better than that in the single-layer biaxial compensation architecture in FIG. 1, the cost of the two-layer biaxial compensation architecture in FIG. 2 is expensive and the improved effect is limited.
Consequently, when the single-layer biaxial compensation architecture in FIG. 1 is utilized under cost consideration, there is a need to solve the problem that the dark-state light leakage is serious in the area near the horizontal viewing angle in the conventional single-layer biaxial compensation architecture.